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1 | \input texinfo @c -*- texinfo -*- |
2 | @c %**start of header | |
ac97a16b | 3 | @setfilename ../../info/nxml-mode |
8cd39fb3 MH |
4 | @settitle nXML Mode |
5 | @c %**end of header | |
6 | ||
7 | @dircategory Emacs | |
8 | @direntry | |
559764ab | 9 | * nXML Mode: (nxml-mode.info). XML editing mode with RELAX NG support. |
8cd39fb3 MH |
10 | @end direntry |
11 | ||
12 | @node Top | |
13 | @top nXML Mode | |
14 | ||
15 | This manual documents nxml-mode, an Emacs major mode for editing | |
16 | XML with RELAX NG support. This manual is not yet complete. | |
17 | ||
18 | @menu | |
19 | * Completion:: | |
20 | * Inserting end-tags:: | |
21 | * Paragraphs:: | |
22 | * Outlining:: | |
23 | * Locating a schema:: | |
24 | * DTDs:: | |
25 | * Limitations:: | |
26 | @end menu | |
27 | ||
28 | @node Completion | |
29 | @chapter Completion | |
30 | ||
31 | Apart from real-time validation, the most important feature that | |
32 | nxml-mode provides for assisting in document creation is "completion". | |
33 | Completion assists the user in inserting characters at point, based on | |
34 | knowledge of the schema and on the contents of the buffer before | |
35 | point. | |
36 | ||
37 | The traditional GNU Emacs key combination for completion in a | |
38 | buffer is @kbd{M-@key{TAB}}. However, many window systems | |
39 | and window managers use this key combination themselves (typically for | |
40 | switching between windows) and do not pass it to applications. It's | |
41 | hard to find key combinations in GNU Emacs that are both easy to type | |
42 | and not taken by something else. @kbd{C-@key{RET}} (i.e. | |
43 | pressing the Enter or Return key, while the Ctrl key is held down) is | |
44 | available. It won't be available on a traditional terminal (because | |
45 | it is indistinguishable from Return), but it will work with a window | |
46 | system. Therefore we adopt the following solution by default: use | |
47 | @kbd{C-@key{RET}} when there's a window system and | |
48 | @kbd{M-@key{TAB}} when there's not. In the following, I | |
49 | will assume that a window system is being used and will therefore | |
50 | refer to @kbd{C-@key{RET}}. | |
51 | ||
52 | Completion works by examining the symbol preceding point. This | |
53 | is the symbol to be completed. The symbol to be completed may be the | |
54 | empty. Completion considers what symbols starting with the symbol to | |
55 | be completed would be valid replacements for the symbol to be | |
56 | completed, given the schema and the contents of the buffer before | |
57 | point. These symbols are the possible completions. An example may | |
58 | make this clearer. Suppose the buffer looks like this (where @point{} | |
59 | indicates point): | |
60 | ||
61 | @example | |
62 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
63 | <h@point{} | |
64 | @end example | |
65 | ||
66 | @noindent | |
67 | and the schema is XHTML. In this context, the symbol to be completed | |
68 | is @samp{h}. The possible completions consist of just | |
69 | @samp{head}. Another example, is | |
70 | ||
71 | @example | |
72 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
73 | <head> | |
74 | <@point{} | |
75 | @end example | |
76 | ||
77 | @noindent | |
78 | In this case, the symbol to be completed is empty, and the possible | |
79 | completions are @samp{base}, @samp{isindex}, | |
80 | @samp{link}, @samp{meta}, @samp{script}, | |
81 | @samp{style}, @samp{title}. Another example is: | |
82 | ||
83 | @example | |
84 | <html xmlns="@point{} | |
85 | @end example | |
86 | ||
87 | @noindent | |
88 | In this case, the symbol to be completed is empty, and the possible | |
89 | completions are just @samp{http://www.w3.org/1999/xhtml}. | |
90 | ||
91 | When you type @kbd{C-@key{RET}}, what happens depends | |
92 | on what the set of possible completions are. | |
93 | ||
94 | @itemize @bullet | |
95 | @item | |
96 | If the set of completions is empty, nothing | |
97 | happens. | |
98 | @item | |
99 | If there is one possible completion, then that completion is | |
100 | inserted, together with any following characters that are | |
101 | required. For example, in this case: | |
102 | ||
103 | @example | |
104 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
105 | <@point{} | |
106 | @end example | |
107 | ||
108 | @noindent | |
109 | @kbd{C-@key{RET}} will yield | |
110 | ||
111 | @example | |
112 | <html xmlns="http://www.w3.org/1999/xhtml"> | |
113 | <head@point{} | |
114 | @end example | |
115 | @item | |
116 | If there is more than one possible completion, but all | |
117 | possible completions share a common non-empty prefix, then that prefix | |
118 | is inserted. For example, suppose the buffer is: | |
119 | ||
120 | @example | |
121 | <html x@point{} | |
122 | @end example | |
123 | ||
124 | @noindent | |
125 | The symbol to be completed is @samp{x}. The possible completions | |
126 | are @samp{xmlns} and @samp{xml:lang}. These share a | |
127 | common prefix of @samp{xml}. Thus, @kbd{C-@key{RET}} | |
128 | will yield: | |
129 | ||
130 | @example | |
131 | <html xml@point{} | |
132 | @end example | |
133 | ||
134 | @noindent | |
135 | Typically, you would do @kbd{C-@key{RET}} again, which would | |
136 | have the result described in the next item. | |
137 | @item | |
138 | If there is more than one possible completion, but the | |
139 | possible completions do not share a non-empty prefix, then Emacs will | |
140 | prompt you to input the symbol in the minibuffer, initializing the | |
141 | minibuffer with the symbol to be completed, and popping up a buffer | |
142 | showing the possible completions. You can now input the symbol to be | |
143 | inserted. The symbol you input will be inserted in the buffer instead | |
144 | of the symbol to be completed. Emacs will then insert any required | |
145 | characters after the symbol. For example, if it contains: | |
146 | ||
147 | @example | |
148 | <html xml@point{} | |
149 | @end example | |
150 | ||
151 | @noindent | |
152 | Emacs will prompt you in the minibuffer with | |
153 | ||
154 | @example | |
155 | Attribute: xml@point{} | |
156 | @end example | |
157 | ||
158 | @noindent | |
159 | and the buffer showing possible completions will contain | |
160 | ||
161 | @example | |
162 | Possible completions are: | |
163 | xml:lang xmlns | |
164 | @end example | |
165 | ||
166 | @noindent | |
167 | If you input @kbd{xmlns}, the result will be: | |
168 | ||
169 | @example | |
170 | <html xmlns="@point{} | |
171 | @end example | |
172 | ||
173 | @noindent | |
174 | (If you do @kbd{C-@key{RET}} again, the namespace URI will | |
175 | be inserted. Should that happen automatically?) | |
176 | @end itemize | |
177 | ||
178 | @node Inserting end-tags | |
179 | @chapter Inserting end-tags | |
180 | ||
181 | The main redundancy in XML syntax is end-tags. nxml-mode provides | |
182 | several ways to make it easier to enter end-tags. You can use all of | |
183 | these without a schema. | |
184 | ||
185 | You can use @kbd{C-@key{RET}} after @samp{</} | |
186 | to complete the rest of the end-tag. | |
187 | ||
188 | @kbd{C-c C-f} inserts an end-tag for the element containing | |
189 | point. This command is useful when you want to input the start-tag, | |
190 | then input the content and finally input the end-tag. The @samp{f} | |
191 | is mnemonic for finish. | |
192 | ||
193 | If you want to keep tags balanced and input the end-tag at the | |
194 | same time as the start-tag, before inputting the content, then you can | |
195 | use @kbd{C-c C-i}. This inserts a @samp{>}, then inserts | |
196 | the end-tag and leaves point before the end-tag. @kbd{C-c C-b} | |
197 | is similar but more convenient for block-level elements: it puts the | |
198 | start-tag, point and the end-tag on successive lines, appropriately | |
199 | indented. The @samp{i} is mnemonic for inline and the | |
200 | @samp{b} is mnemonic for block. | |
201 | ||
202 | Finally, you can customize nxml-mode so that @kbd{/} | |
203 | automatically inserts the rest of the end-tag when it occurs after | |
204 | @samp{<}, by doing | |
205 | ||
206 | @display | |
207 | @kbd{M-x customize-variable @key{RET} nxml-slash-auto-complete-flag @key{RET}} | |
208 | @end display | |
209 | ||
210 | @noindent | |
211 | and then following the instructions in the displayed buffer. | |
212 | ||
213 | @node Paragraphs | |
214 | @chapter Paragraphs | |
215 | ||
216 | Emacs has several commands that operate on paragraphs, most | |
217 | notably @kbd{M-q}. nXML mode redefines these to work in a way | |
218 | that is useful for XML. The exact rules that are used to find the | |
219 | beginning and end of a paragraph are complicated; they are designed | |
220 | mainly to ensure that @kbd{M-q} does the right thing. | |
221 | ||
222 | A paragraph consists of one or more complete, consecutive lines. | |
223 | A group of lines is not considered a paragraph unless it contains some | |
224 | non-whitespace characters between tags or inside comments. A blank | |
225 | line separates paragraphs. A single tag on a line by itself also | |
226 | separates paragraphs. More precisely, if one tag together with any | |
227 | leading and trailing whitespace completely occupy one or more lines, | |
228 | then those lines will not be included in any paragraph. | |
229 | ||
230 | A start-tag at the beginning of the line (possibly indented) may | |
231 | be treated as starting a paragraph. Similarly, an end-tag at the end | |
232 | of the line may be treated as ending a paragraph. The following rules | |
233 | are used to determine whether such a tag is in fact treated as a | |
234 | paragraph boundary: | |
235 | ||
236 | @itemize @bullet | |
237 | @item | |
238 | If the schema does not allow text at that point, then it | |
239 | is a paragraph boundary. | |
240 | @item | |
241 | If the end-tag corresponding to the start-tag is not at | |
242 | the end of its line, or the start-tag corresponding to the end-tag is | |
243 | not at the beginning of its line, then it is not a paragraph | |
244 | boundary. For example, in | |
245 | ||
246 | @example | |
247 | <p>This is a paragraph with an | |
248 | <emph>emphasized</emph> phrase. | |
249 | @end example | |
250 | ||
251 | @noindent | |
252 | the @samp{<emph>} start-tag would not be considered as | |
253 | starting a paragraph, because its corresponding end-tag is not at the | |
254 | end of the line. | |
255 | @item | |
256 | If there is text that is a sibling in element tree, then | |
257 | it is not a paragraph boundary. For example, in | |
258 | ||
259 | @example | |
260 | <p>This is a paragraph with an | |
261 | <emph>emphasized phrase that takes one source line</emph> | |
262 | @end example | |
263 | ||
264 | @noindent | |
265 | the @samp{<emph>} start-tag would not be considered as | |
266 | starting a paragraph, even though its end-tag is at the end of its | |
267 | line, because there the text @samp{This is a paragraph with an} | |
268 | is a sibling of the @samp{emph} element. | |
269 | @item | |
270 | Otherwise, it is a paragraph boundary. | |
271 | @end itemize | |
272 | ||
273 | @node Outlining | |
274 | @chapter Outlining | |
275 | ||
276 | nXML mode allows you to display all or part of a buffer as an | |
277 | outline, in a similar way to Emacs' outline mode. An outline in nXML | |
278 | mode is based on recognizing two kinds of element: sections and | |
279 | headings. There is one heading for every section and one section for | |
280 | every heading. A section contains its heading as or within its first | |
281 | child element. A section also contains its subordinate sections (its | |
282 | subsections). The text content of a section consists of anything in a | |
283 | section that is neither a subsection nor a heading. | |
284 | ||
285 | Note that this is a different model from that used by XHTML. | |
286 | nXML mode's outline support will not be useful for XHTML unless you | |
287 | adopt a convention of adding a @code{div} to enclose each | |
288 | section, rather than having sections implicitly delimited by different | |
289 | @code{h@var{n}} elements. This limitation may be removed | |
290 | in a future version. | |
291 | ||
292 | The variable @code{nxml-section-element-name-regexp} gives | |
293 | a regexp for the local names (i.e. the part of the name following any | |
294 | prefix) of section elements. The variable | |
295 | @code{nxml-heading-element-name-regexp} gives a regexp for the | |
296 | local names of heading elements. For an element to be recognized | |
297 | as a section | |
298 | ||
299 | @itemize @bullet | |
300 | @item | |
301 | its start-tag must occur at the beginning of a line | |
302 | (possibly indented); | |
303 | @item | |
304 | its local name must match | |
305 | @code{nxml-section-element-name-regexp}; | |
306 | @item | |
307 | either its first child element or a descendant of that | |
308 | first child element must have a local name that matches | |
309 | @code{nxml-heading-element-name-regexp}; the first such element | |
310 | is treated as the section's heading. | |
311 | @end itemize | |
312 | ||
313 | @noindent | |
314 | You can customize these variables using @kbd{M-x | |
315 | customize-variable}. | |
316 | ||
317 | There are three possible outline states for a section: | |
318 | ||
319 | @itemize @bullet | |
320 | @item | |
321 | normal, showing everything, including its heading, text | |
322 | content and subsections; each subsection is displayed according to the | |
323 | state of that subsection; | |
324 | @item | |
325 | showing just its heading, with both its text content and | |
326 | its subsections hidden; all subsections are hidden regardless of their | |
327 | state; | |
328 | @item | |
329 | showing its heading and its subsections, with its text | |
330 | content hidden; each subsection is displayed according to the state of | |
331 | that subsection. | |
332 | @end itemize | |
333 | ||
334 | In the last two states, where the text content is hidden, the | |
335 | heading is displayed specially, in an abbreviated form. An element | |
336 | like this: | |
337 | ||
338 | @example | |
339 | <section> | |
340 | <title>Food</title> | |
341 | <para>There are many kinds of food.</para> | |
342 | </section> | |
343 | @end example | |
344 | ||
345 | @noindent | |
346 | would be displayed on a single line like this: | |
347 | ||
348 | @example | |
349 | <-section>Food...</> | |
350 | @end example | |
351 | ||
352 | @noindent | |
353 | If there are hidden subsections, then a @code{+} will be used | |
354 | instead of a @code{-} like this: | |
355 | ||
356 | @example | |
357 | <+section>Food...</> | |
358 | @end example | |
359 | ||
360 | @noindent | |
361 | If there are non-hidden subsections, then the section will instead be | |
362 | displayed like this: | |
363 | ||
364 | @example | |
365 | <-section>Food... | |
366 | <-section>Delicious Food...</> | |
367 | <-section>Distasteful Food...</> | |
368 | </-section> | |
369 | @end example | |
370 | ||
371 | @noindent | |
372 | The heading is always displayed with an indent that corresponds to its | |
373 | depth in the outline, even it is not actually indented in the buffer. | |
374 | The variable @code{nxml-outline-child-indent} controls how much | |
375 | a subheading is indented with respect to its parent heading when the | |
376 | heading is being displayed specially. | |
377 | ||
378 | Commands to change the outline state of sections are bound to | |
379 | key sequences that start with @kbd{C-c C-o} (@kbd{o} is | |
380 | mnemonic for outline). The third and final key has been chosen to be | |
381 | consistent with outline mode. In the following descriptions | |
382 | current section means the section containing point, or, more precisely, | |
383 | the innermost section containing the character immediately following | |
384 | point. | |
385 | ||
386 | @itemize @bullet | |
387 | @item | |
388 | @kbd{C-c C-o C-a} shows all sections in the buffer | |
389 | normally. | |
390 | @item | |
391 | @kbd{C-c C-o C-t} hides the text content | |
392 | of all sections in the buffer. | |
393 | @item | |
394 | @kbd{C-c C-o C-c} hides the text content | |
395 | of the current section. | |
396 | @item | |
397 | @kbd{C-c C-o C-e} shows the text content | |
398 | of the current section. | |
399 | @item | |
400 | @kbd{C-c C-o C-d} hides the text content | |
401 | and subsections of the current section. | |
402 | @item | |
403 | @kbd{C-c C-o C-s} shows the current section | |
404 | and all its direct and indirect subsections normally. | |
405 | @item | |
406 | @kbd{C-c C-o C-k} shows the headings of the | |
407 | direct and indirect subsections of the current section. | |
408 | @item | |
409 | @kbd{C-c C-o C-l} hides the text content of the | |
410 | current section and of its direct and indirect | |
411 | subsections. | |
412 | @item | |
413 | @kbd{C-c C-o C-i} shows the headings of the | |
414 | direct subsections of the current section. | |
415 | @item | |
416 | @kbd{C-c C-o C-o} hides as much as possible without | |
417 | hiding the current section's text content; the headings of ancestor | |
418 | sections of the current section and their child section sections will | |
419 | not be hidden. | |
420 | @end itemize | |
421 | ||
422 | When a heading is displayed specially, you can use | |
423 | @key{RET} in that heading to show the text content of the section | |
424 | in the same way as @kbd{C-c C-o C-e}. | |
425 | ||
426 | You can also use the mouse to change the outline state: | |
427 | @kbd{S-mouse-2} hides the text content of a section in the same | |
428 | way as@kbd{C-c C-o C-c}; @kbd{mouse-2} on a specially | |
429 | displayed heading shows the text content of the section in the same | |
430 | way as @kbd{C-c C-o C-e}; @kbd{mouse-1} on a specially | |
431 | displayed start-tag toggles the display of subheadings on and | |
432 | off. | |
433 | ||
434 | The outline state for each section is stored with the first | |
435 | character of the section (as a text property). Every command that | |
436 | changes the outline state of any section updates the display of the | |
437 | buffer so that each section is displayed correctly according to its | |
438 | outline state. If the section structure is subsequently changed, then | |
439 | it is possible for the display to no longer correctly reflect the | |
440 | stored outline state. @kbd{C-c C-o C-r} can be used to refresh | |
441 | the display so it is correct again. | |
442 | ||
443 | @node Locating a schema | |
444 | @chapter Locating a schema | |
445 | ||
446 | nXML mode has a configurable set of rules to locate a schema for | |
447 | the file being edited. The rules are contained in one or more schema | |
448 | locating files, which are XML documents. | |
449 | ||
450 | The variable @samp{rng-schema-locating-files} specifies | |
451 | the list of the file-names of schema locating files that nXML mode | |
452 | should use. The order of the list is significant: when file | |
453 | @var{x} occurs in the list before file @var{y} then rules | |
454 | from file @var{x} have precedence over rules from file | |
455 | @var{y}. A filename specified in | |
456 | @samp{rng-schema-locating-files} may be relative. If so, it will | |
457 | be resolved relative to the document for which a schema is being | |
458 | located. It is not an error if relative file-names in | |
459 | @samp{rng-schema-locating-files} do not not exist. You can use | |
460 | @kbd{M-x customize-variable @key{RET} rng-schema-locating-files | |
461 | @key{RET}} to customize the list of schema locating | |
462 | files. | |
463 | ||
464 | By default, @samp{rng-schema-locating-files} list has two | |
465 | members: @samp{schemas.xml}, and | |
466 | @samp{@var{dist-dir}/schema/schemas.xml} where | |
467 | @samp{@var{dist-dir}} is the directory containing the nXML | |
468 | distribution. The first member will cause nXML mode to use a file | |
469 | @samp{schemas.xml} in the same directory as the document being | |
470 | edited if such a file exist. The second member contains rules for the | |
471 | schemas that are included with the nXML distribution. | |
472 | ||
473 | @menu | |
474 | * Commands for locating a schema:: | |
475 | * Schema locating files:: | |
476 | @end menu | |
477 | ||
478 | @node Commands for locating a schema | |
479 | @section Commands for locating a schema | |
480 | ||
481 | The command @kbd{C-c C-s C-w} will tell you what schema | |
482 | is currently being used. | |
483 | ||
484 | The rules for locating a schema are applied automatically when | |
485 | you visit a file in nXML mode. However, if you have just created a new | |
486 | file and the schema cannot be inferred from the file-name, then this | |
487 | will not locate the right schema. In this case, you should insert the | |
488 | start-tag of the root element and then use the command @kbd{C-c | |
489 | C-a}, which reapplies the rules based on the current content of | |
490 | the document. It is usually not necessary to insert the complete | |
491 | start-tag; often just @samp{<@var{name}} is | |
492 | enough. | |
493 | ||
494 | If you want to use a schema that has not yet been added to the | |
495 | schema locating files, you can use the command @kbd{C-c C-s C-f} | |
496 | to manually select the file contaiing the schema for the document in | |
497 | current buffer. Emacs will read the file-name of the schema from the | |
498 | minibuffer. After reading the file-name, Emacs will ask whether you | |
499 | wish to add a rule to a schema locating file that persistently | |
500 | associates the document with the selected schema. The rule will be | |
501 | added to the first file in the list specified | |
502 | @samp{rng-schema-locating-files}; it will create the file if | |
503 | necessary, but will not create a directory. If the variable | |
504 | @samp{rng-schema-locating-files} has not been customized, this | |
505 | means that the rule will be added to the file @samp{schemas.xml} | |
506 | in the same directory as the document being edited. | |
507 | ||
508 | The command @kbd{C-c C-s C-t} allows you to select a schema by | |
509 | specifying an identifier for the type of the document. The schema | |
510 | locating files determine the available type identifiers and what | |
511 | schema is used for each type identifier. This is useful when it is | |
512 | impossible to infer the right schema from either the file-name or the | |
513 | content of the document, even though the schema is already in the | |
514 | schema locating file. A situation in which this can occur is when | |
515 | there are multiple variants of a schema where all valid documents have | |
516 | the same document element. For example, XHTML has Strict and | |
517 | Transitional variants. In a situation like this, a schema locating file | |
518 | can define a type identifier for each variant. As with @kbd{C-c | |
519 | C-s C-f}, Emacs will ask whether you wish to add a rule to a schema | |
520 | locating file that persistently associates the document with the | |
521 | specified type identifier. | |
522 | ||
523 | The command @kbd{C-c C-s C-l} adds a rule to a schema | |
524 | locating file that persistently associates the document with | |
525 | the schema that is currently being used. | |
526 | ||
527 | @node Schema locating files | |
528 | @section Schema locating files | |
529 | ||
530 | Each schema locating file specifies a list of rules. The rules | |
531 | from each file are appended in order. To locate a schema each rule is | |
532 | applied in turn until a rule matches. The first matching rule is then | |
533 | used to determine the schema. | |
534 | ||
535 | Schema locating files are designed to be useful for other | |
536 | applications that need to locate a schema for a document. In fact, | |
537 | there is nothing specific to locating schemas in the design; it could | |
538 | equally well be used for locating a stylesheet. | |
539 | ||
540 | @menu | |
541 | * Schema locating file syntax basics:: | |
542 | * Using the document's URI to locate a schema:: | |
543 | * Using the document element to locate a schema:: | |
544 | * Using type identifiers in schema locating files:: | |
545 | * Using multiple schema locating files:: | |
546 | @end menu | |
547 | ||
548 | @node Schema locating file syntax basics | |
549 | @subsection Schema locating file syntax basics | |
550 | ||
551 | There is a schema for schema locating files in the file | |
552 | @samp{locate.rnc} in the schema directory. Schema locating | |
553 | files must be valid with respect to this schema. | |
554 | ||
555 | The document element of a schema locating file must be | |
556 | @samp{locatingRules} and the namespace URI must be | |
557 | @samp{http://thaiopensource.com/ns/locating-rules/1.0}. The | |
558 | children of the document element specify rules. The order of the | |
559 | children is the same as the order of the rules. Here's a complete | |
560 | example of a schema locating file: | |
561 | ||
562 | @example | |
563 | <?xml version="1.0"?> | |
564 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
565 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
566 | <documentElement localName="book" uri="docbook.rnc"/> | |
567 | </locatingRules> | |
568 | @end example | |
569 | ||
570 | @noindent | |
571 | This says to use the schema @samp{xhtml.rnc} for a document with | |
572 | namespace @samp{http://www.w3.org/1999/xhtml}, and to use the | |
573 | schema @samp{docbook.rnc} for a document whose local name is | |
574 | @samp{book}. If the document element had both a namespace URI | |
575 | of @samp{http://www.w3.org/1999/xhtml} and a local name of | |
576 | @samp{book}, then the matching rule that comes first will be | |
577 | used and so the schema @samp{xhtml.rnc} would be used. There is | |
578 | no precedence between different types of rule; the first matching rule | |
579 | of any type is used. | |
580 | ||
581 | As usual with XML-related technologies, resources are identified | |
582 | by URIs. The @samp{uri} attribute identifies the schema by | |
583 | specifying the URI. The URI may be relative. If so, it is resolved | |
584 | relative to the URI of the schema locating file that contains | |
585 | attribute. This means that if the value of @samp{uri} attribute | |
586 | does not contain a @samp{/}, then it will refer to a filename in | |
587 | the same directory as the schema locating file. | |
588 | ||
589 | @node Using the document's URI to locate a schema | |
590 | @subsection Using the document's URI to locate a schema | |
591 | ||
592 | A @samp{uri} rule locates a schema based on the URI of the | |
593 | document. The @samp{uri} attribute specifies the URI of the | |
594 | schema. The @samp{resource} attribute can be used to specify | |
595 | the schema for a particular document. For example, | |
596 | ||
597 | @example | |
598 | <uri resource="spec.xml" uri="docbook.rnc"/> | |
599 | @end example | |
600 | ||
601 | @noindent | |
602 | specifies that that the schema for @samp{spec.xml} is | |
603 | @samp{docbook.rnc}. | |
604 | ||
605 | The @samp{pattern} attribute can be used instead of the | |
606 | @samp{resource} attribute to specify the schema for any document | |
607 | whose URI matches a pattern. The pattern has the same syntax as an | |
608 | absolute or relative URI except that the path component of the URI can | |
609 | use a @samp{*} character to stand for zero or more characters | |
610 | within a path segment (i.e. any character other @samp{/}). | |
611 | Typically, the URI pattern looks like a relative URI, but, whereas a | |
612 | relative URI in the @samp{resource} attribute is resolved into a | |
613 | particular absolute URI using the base URI of the schema locating | |
614 | file, a relative URI pattern matches if it matches some number of | |
615 | complete path segments of the document's URI ending with the last path | |
616 | segment of the document's URI. For example, | |
617 | ||
618 | @example | |
619 | <uri pattern="*.xsl" uri="xslt.rnc"/> | |
620 | @end example | |
621 | ||
622 | @noindent | |
623 | specifies that the schema for documents with a URI whose path ends | |
624 | with @samp{.xsl} is @samp{xslt.rnc}. | |
625 | ||
626 | A @samp{transformURI} rule locates a schema by | |
627 | transforming the URI of the document. The @samp{fromPattern} | |
628 | attribute specifies a URI pattern with the same meaning as the | |
629 | @samp{pattern} attribute of the @samp{uri} element. The | |
630 | @samp{toPattern} attribute is a URI pattern that is used to | |
631 | generate the URI of the schema. Each @samp{*} in the | |
632 | @samp{toPattern} is replaced by the string that matched the | |
633 | corresponding @samp{*} in the @samp{fromPattern}. The | |
634 | resulting string is appended to the initial part of the document's URI | |
635 | that was not explicitly matched by the @samp{fromPattern}. The | |
636 | rule matches only if the transformed URI identifies an existing | |
637 | resource. For example, the rule | |
638 | ||
639 | @example | |
640 | <transformURI fromPattern="*.xml" toPattern="*.rnc"/> | |
641 | @end example | |
642 | ||
643 | @noindent | |
644 | would transform the URI @samp{file:///home/jjc/docs/spec.xml} | |
645 | into the URI @samp{file:///home/jjc/docs/spec.rnc}. Thus, this | |
646 | rule specifies that to locate a schema for a document | |
647 | @samp{@var{foo}.xml}, Emacs should test whether a file | |
648 | @samp{@var{foo}.rnc} exists in the same directory as | |
649 | @samp{@var{foo}.xml}, and, if so, should use it as the | |
650 | schema. | |
651 | ||
652 | @node Using the document element to locate a schema | |
653 | @subsection Using the document element to locate a schema | |
654 | ||
655 | A @samp{documentElement} rule locates a schema based on | |
656 | the local name and prefix of the document element. For example, a rule | |
657 | ||
658 | @example | |
659 | <documentElement prefix="xsl" localName="stylesheet" uri="xslt.rnc"/> | |
660 | @end example | |
661 | ||
662 | @noindent | |
663 | specifies that when the name of the document element is | |
664 | @samp{xsl:stylesheet}, then @samp{xslt.rnc} should be used | |
665 | as the schema. Either the @samp{prefix} or | |
666 | @samp{localName} attribute may be omitted to allow any prefix or | |
667 | local name. | |
668 | ||
669 | A @samp{namespace} rule locates a schema based on the | |
670 | namespace URI of the document element. For example, a rule | |
671 | ||
672 | @example | |
673 | <namespace ns="http://www.w3.org/1999/XSL/Transform" uri="xslt.rnc"/> | |
674 | @end example | |
675 | ||
676 | @noindent | |
677 | specifies that when the namespace URI of the document is | |
678 | @samp{http://www.w3.org/1999/XSL/Transform}, then | |
679 | @samp{xslt.rnc} should be used as the schema. | |
680 | ||
681 | @node Using type identifiers in schema locating files | |
682 | @subsection Using type identifiers in schema locating files | |
683 | ||
684 | Type identifiers allow a level of indirection in locating the | |
685 | schema for a document. Instead of associating the document directly | |
686 | with a schema URI, the document is associated with a type identifier, | |
687 | which is in turn associated with a schema URI. nXML mode does not | |
688 | constrain the format of type identifiers. They can be simply strings | |
689 | without any formal structure or they can be public identifiers or | |
690 | URIs. Note that these type identifiers have nothing to do with the | |
691 | DOCTYPE declaration. When comparing type identifiers, whitespace is | |
692 | normalized in the same way as with the @samp{xsd:token} | |
693 | datatype: leading and trailing whitespace is stripped; other sequences | |
694 | of whitespace are normalized to a single space character. | |
695 | ||
696 | Each of the rules described in previous sections that uses a | |
697 | @samp{uri} attribute to specify a schema, can instead use a | |
698 | @samp{typeId} attribute to specify a type identifier. The type | |
699 | identifier can be associated with a URI using a @samp{typeId} | |
700 | element. For example, | |
701 | ||
702 | @example | |
703 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
704 | <namespace ns="http://www.w3.org/1999/xhtml" typeId="XHTML"/> | |
705 | <typeId id="XHTML" typeId="XHTML Strict"/> | |
706 | <typeId id="XHTML Strict" uri="xhtml-strict.rnc"/> | |
707 | <typeId id="XHTML Transitional" uri="xhtml-transitional.rnc"/> | |
708 | </locatingRules> | |
709 | @end example | |
710 | ||
711 | @noindent | |
712 | declares three type identifiers @samp{XHTML} (representing the | |
713 | default variant of XHTML to be used), @samp{XHTML Strict} and | |
714 | @samp{XHTML Transitional}. Such a schema locating file would | |
715 | use @samp{xhtml-strict.rnc} for a document whose namespace is | |
716 | @samp{http://www.w3.org/1999/xhtml}. But it is considerably | |
717 | more flexible than a schema locating file that simply specified | |
718 | ||
719 | @example | |
720 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml-strict.rnc"/> | |
721 | @end example | |
722 | ||
723 | @noindent | |
724 | A user can easily use @kbd{C-c C-s C-t} to select between XHTML | |
725 | Strict and XHTML Transitional. Also, a user can easily add a catalog | |
726 | ||
727 | @example | |
728 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
729 | <typeId id="XHTML" typeId="XHTML Transitional"/> | |
730 | </locatingRules> | |
731 | @end example | |
732 | ||
733 | @noindent | |
734 | that makes the default variant of XHTML be XHTML Transitional. | |
735 | ||
736 | @node Using multiple schema locating files | |
737 | @subsection Using multiple schema locating files | |
738 | ||
739 | The @samp{include} element includes rules from another | |
740 | schema locating file. The behavior is exactly as if the rules from | |
741 | that file were included in place of the @samp{include} element. | |
742 | Relative URIs are resolved into absolute URIs before the inclusion is | |
743 | performed. For example, | |
744 | ||
745 | @example | |
746 | <include rules="../rules.xml"/> | |
747 | @end example | |
748 | ||
749 | @noindent | |
750 | includes the rules from @samp{rules.xml}. | |
751 | ||
752 | The process of locating a schema takes as input a list of schema | |
753 | locating files. The rules in all these files and in the files they | |
754 | include are resolved into a single list of rules, which are applied | |
755 | strictly in order. Sometimes this order is not what is needed. | |
756 | For example, suppose you have two schema locating files, a private | |
757 | file | |
758 | ||
759 | @example | |
760 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
761 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
762 | </locatingRules> | |
763 | @end example | |
764 | ||
765 | @noindent | |
766 | followed by a public file | |
767 | ||
768 | @example | |
769 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
770 | <transformURI pathSuffix=".xml" replacePathSuffix=".rnc"/> | |
771 | <namespace ns="http://www.w3.org/1999/XSL/Transform" typeId="XSLT"/> | |
772 | </locatingRules> | |
773 | @end example | |
774 | ||
775 | @noindent | |
776 | The effect of these two files is that the XHTML @samp{namespace} | |
777 | rule takes precedence over the @samp{transformURI} rule, which | |
778 | is almost certainly not what is needed. This can be solved by adding | |
779 | an @samp{applyFollowingRules} to the private file. | |
780 | ||
781 | @example | |
782 | <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> | |
783 | <applyFollowingRules ruleType="transformURI"/> | |
784 | <namespace ns="http://www.w3.org/1999/xhtml" uri="xhtml.rnc"/> | |
785 | </locatingRules> | |
786 | @end example | |
787 | ||
788 | @node DTDs | |
789 | @chapter DTDs | |
790 | ||
791 | nxml-mode is designed to support the creation of standalone XML | |
792 | documents that do not depend on a DTD. Although it is common practice | |
793 | to insert a DOCTYPE declaration referencing an external DTD, this has | |
794 | undesirable side-effects. It means that the document is no longer | |
795 | self-contained. It also means that different XML parsers may interpret | |
796 | the document in different ways, since the XML Recommendation does not | |
797 | require XML parsers to read the DTD. With DTDs, it was impractical to | |
798 | get validation without using an external DTD or reference to an | |
799 | parameter entity. With RELAX NG and other schema languages, you can | |
800 | simulataneously get the benefits of validation and standalone XML | |
801 | documents. Therefore, I recommend that you do not reference an | |
802 | external DOCTYPE in your XML documents. | |
803 | ||
804 | One problem is entities for characters. Typically, as well as | |
805 | providing validation, DTDs also provide a set of character entities | |
806 | for documents to use. Schemas cannot provide this functionality, | |
807 | because schema validation happens after XML parsing. The recommended | |
808 | solution is to either use the Unicode characters directly, or, if this | |
809 | is impractical, use character references. nXML mode supports this by | |
810 | providing commands for entering characters and character references | |
811 | using the Unicode names, and can display the glyph corresponding to a | |
812 | character reference. | |
813 | ||
814 | @node Limitations | |
815 | @chapter Limitations | |
816 | ||
817 | nXML mode has some limitations: | |
818 | ||
819 | @itemize @bullet | |
820 | @item | |
821 | DTD support is limited. Internal parsed general entities declared | |
822 | in the internal subset are supported provided they do not contain | |
823 | elements. Other usage of DTDs is ignored. | |
824 | @item | |
825 | The restrictions on RELAX NG schemas in section 7 of the RELAX NG | |
826 | specification are not enforced. | |
827 | @item | |
828 | Unicode support has problems. This stems mostly from the fact that | |
829 | the XML (and RELAX NG) character model is based squarely on Unicode, | |
830 | whereas the Emacs character model is not. Emacs 22 is slated to have | |
831 | full Unicode support, which should improve the situation here. | |
832 | @end itemize | |
833 | ||
834 | @bye | |
ab4c34c6 MB |
835 | |
836 | @ignore | |
837 | arch-tag: 3b6e8ac2-ae8d-4f38-bd43-ce9f80be04d6 | |
838 | @end ignore |